Extended dynamic resource allocation in packet data transfer

ABSTRACT

A method for control of packet data transmissions in a TDMA wireless network to provide for additional choices in the allocation of communication channels. The fixed relationship in the timing of the downlink allocation signalling and subsequent uplink transmission is altered for certain classes of mobile station to avoid physical constraints. Examples of variations in USF signalling in GPRS are given.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to multiple access communication systemsand in particular it relates to dynamic resource allocation in timedivision multiple access systems.

[0003] 2. Description of Related Art

[0004] In Multiple access wireless systems such as GSM, a number ofmobile stations communicate with a network. The allocation of physicalcommunication channels for use by the mobile stations is fixed. Adescription of the GSM system may be found in The GSM System for MobileCommunications by M. Mouly and M. B. Pautet, published 1992 with theISBN reference 2-9507190-0-7.

[0005] With the advent of packet data communications over Time DivisionMultiple Access (TDMA) systems, more flexibility is required in theallocation of resources and in particular in the use of physicalcommunication channels. For packet data transmissions in General PacketRadio Systems (GPRS) a number of Packet Data CHannels (PDCH) provide thephysical communication links. The time division is by frames of 4.615 msduration and each frame has eight consecutive 0.577 ms slots. Adescription of the GPRS system may be found in (3GPP TS 43.064 v5.1.1).The slots may be used for uplink or downlink communication. Uplinkcommunication is a transmission from the mobile station for reception bythe network to which it is attached. Reception by the mobile station ofa transmission from the network is described as downlink.

[0006] In order to utilise most effectively the available bandwidth,access to channels can be allocated in response to changes in channelconditions, traffic loading, Quality of Service and subscription class.Owing to the continually changing channel conditions and trafficloadings a method for dynamic allocation of the available channels isavailable.

[0007] The amounts of time that the mobile station receives downlink ortransmits uplink may be varied and slots allocated accordingly. Thesequences of slots allocated for reception and transmission, theso-called multislot pattern is usually described in the form RXTY. Theallocated-receive (R) slots being the number X and the allocatedtransmit slots (T) the number Y.

[0008] A number of multislot classes, one through to 45, is defined forGPRS operation and the maximum uplink (Tx) and downlink (Rx) slotallocations are specified for each class.

[0009] In a GPRS system, access to a shared channel is controlled bymeans of an Uplink Status Flag (USF) transmitted on the downlink to eachcommunicating mobile station (MS). In GPRS two allocation methods aredefined, which differ in the convention about which uplink slots aremade available on receipt of a USF. The present invention relates to aparticular allocation method, in which an equal number “N” of PDCH's, a“PDCH” representing a pair of uplink and downlink slots corresponding toeach other on a 1-1 basis, are allocated for potential use by the MS.The uplink slots available for actual use by a particular mobile stationsharing the uplink channel are indicated in the USF. The USF is a dataitem capable of taking 8 values V0-V7, and allows uplink resources to beallocated amongst up to 8 mobiles where each mobile recognises one ofthese 8 values as ‘valid’, i.e. conferring exclusive use of resources tothat mobile. A particular mobile station may recognise a different USFvalue on each of the slots assigned to that mobile station. In the caseof the extended dynamic allocation method, for example, reception of avalid USF in the slot 2 of the present frame will indicate the actualavailability for transmission of transmit slots 2 . . . N in the nextTDMA frame or group of frames, where N is the number of allocated PDCHs.Generally for a valid USF received at receiver slot n, transmissiontakes place in the next transmit frame at transmit slots n, n+1 et seq.to the allocated number of slots (N). For the extended dynamicallocation method as presently defined these allocated slots are alwaysconsecutive.

[0010] The mobile station is not able instantly to switch from a receivecondition to a transmit condition or vice versa and the time allocatedto these reconfigurations is known as turnaround time. It is alsonecessary for the mobile station, whilst in packet transfer mode, toperform neighbourhood cell measurements. The mobile station hascontinuously to monitor all Broadcast Control Channel (BCCH) carriers asindicated by the BA(GPRS) list and the BCCH carrier of the serving cell.A received signal level measurement sample is taken in every TDMA frame,on at least one of the BCCH carriers. (3GPP TS 45.008v5 10.0). Theturnaround and measurement times guaranteed by the network for a mobilestation depend on the multislot class to which the mobile claimsconformance (3GPP TS 45.002v5.9.0 Annex B).

[0011] The neighbour cell measurements are taken prior tore-configuration from reception to transmission or prior tore-configuration from transmission to reception.

[0012] A mobile station operating in extended dynamic allocation modepresently must begin uplink transmission in the Tx timeslotcorresponding to the Rx timeslot in which the first valid USF isrecognised. That is to say that there is a fixed relationship in thetiming of the downlink allocation signalling and subsequent uplinktransmission. Owing to the physical limitations of single transceivermobile stations some desirable multislot configurations are notavailable for use.

[0013] These restrictions reduce the availability of slots for uplinktransmissions thereby reducing the flow of data and the flexibility ofresponse to changing conditions. There is a need therefore to provide amethod with which to enable the use of those multislot configurationscurrently unavailable for Extended Dynamic Allocation.

SUMMARY OF THE INVENTION

[0014] It is an object of this invention to reduce the restrictionsaffecting extended dynamic allocation with minimal effect on theexisting prescript. This may be achieved by altering the fixedrelationship in the timing of the downlink allocation signalling andsubsequent uplink transmission for certain classes of mobile station.

[0015] In accordance with the invention there is a method forcontrolling uplink packet data transmissions and a mobile stationoperating in accordance with the method as set out in the attachedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] An embodiment of the invention will now be described withreference to the accompanying figures in which:

[0017]FIG. 1 illustrates the GPRS TDMA frame structure showing thenumbering convention used for uplink (UL) and downlink (DL) timeslots;

[0018]FIG. 2 illustrates a prior art 4 slot steady state allocationR1T4;

[0019]FIG. 3 illustrates a 5 slot steady state allocation RLTSprohibited in the prior art;

[0020]FIG. 4 illustrates a 5 slot steady state allocation R1T5 enabledby the method of the present invention;

[0021]FIG. 5 illustrates a shifted USF applied to a class 7 MS with 3uplink slots allocated;

[0022]FIG. 6 illustrates a class 7 MS with 2 uplink slots allocated;

[0023]FIG. 7 is a flow diagram for the implementation of shifted USF ina mobile station;

[0024]FIG. 8 illustrates a transition from one uplink slot to fiveuplink slots for a class 34 MS; and

[0025]FIG. 9 illustrates a transition from four to five uplink slots fora class 34 MS.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] In this embodiment, the invention is applied to a GPRS wirelessnetwork operating in accordance with the standards applicable tomultislot classes.

[0027] In FIG. 1 the GPRS TDMA frame structure is illustrated and showsthe numbering convention used for uplink (Tx) and downlink (Rx)timeslots. It should be noted that in practice Tx may be advancedrelative to Rx due to timing advance (TA), although this is not shown inthe illustration. Thus in practice the amount of time between the firstRx and first Tx of a frame may be reduced a fraction of a slot from theillustrated value of 3 slots due to timing advance.

[0028] Two successive TDMA frames are illustrated with downlink (DL) anduplink (UL) slots identified separately. The slot positions within thefirst frame are shown by the numerals 0 through to 7 with thetransmission and reception slots offset by a margin of three slots. Thisis in accordance with the convention that that the first transmit framein a TDMA lags the first receive frame by an offset of 3 (thus ordinarysingle slot GSM can be regarded as a particular case in which only slot1 of transmit and receive is used).

[0029] The remaining figures conform to the illustration of FIG. 1 butthe slot numbering has been removed for extra clarity. The shaded slotsare those allocated for the particular states and the arrowed insertsindicate the applicable measurement and turnaround intervals. The hashedslots indicate reception of a valid USF and the timeslot in which thatUSF is received. As mentioned above, constraints are imposed by the needto allow measurement and turnaround slots and the prescript for these in3GPP TS 45.002 Annex B limits dynamic allocation as shown in table 1.TABLE 1 Maximum Minimum number of Multislot number of slots slots classRx Tx Sum T_(ta) T_(tb) T_(ra) T_(rb) 7 3 3 4 3 1 3 1 34 5 5 6 2 1 1 139 5 5 6 2 1 1 + to 1 45 6 6 7 1 1 1 to

[0030] T_(ta) is the time needed for the MS to perform adjacent cellsignal level measurement and get ready to transmit.

[0031] T_(tb) is the time needed for the MS to get ready to transmit

[0032] T_(ra) is the time needed for the MS to perform adjacent cellsignal level measurement and get ready to receive.

[0033] T_(rb) is the time needed for the MS to get ready to receive

[0034] It should be noted that in practice the times T_(ta) and T_(tb)may be reduced by a fraction of a slot due to timing advance. t₀ is 31symbol periods timing advance offset

[0035] With reference to FIG. 2, a steady state single downlink and 4uplink slot allocation for a class 34 mobile station is illustrated. Theturnaround and measurement periods for this class are shown in table 1as Tra, Trb and Ttb each having one slot and Tta having two slots. Theseperiods can be accommodated for this allocation when a valid USF isreceived in time slot 0.

[0036] When the allocation of uplink slots extends to five, however, aconstraint arises as indicated in the illustration of FIG. 3 which isfor a class 34 mobile station with an allocation of one downlink andfive uplink slots.

[0037] The constraint occurs at the position indicated by ‘A’ because notime is allowed for the changeover from transmit to receive (Trb). Inthe downlink time slot 0 a valid USF is received and the following twoslots provide for Tta. In accordance with the invention, for thisembodiment the mobile has uplink slots assigned in the usual way,through the use of USF_TN0 . . . USF_TN7 Information Elements in PacketUplink Assignment and Packet Timeslot Reconfigure messages. The networksends the USF, however, for both first and second assigned timeslots onthe downlink PDCH associated with the second assigned timeslot.

[0038] Considering by way of example a class 34 MS with an assignment of5 uplink slots (TN0-TN4) as discussed above where the network sendsUSF_TN0 on timeslot 1 rather than timeslot 0. This arrangement isillustrated in FIG. 4 where it can be seen that slots marked ‘B’ and ‘C’provide for turnaround times Tra and Trb respectively.

[0039] An allocation by the network of 4 uplink slots to the MS will besignalled by the sending of USF_TN1 on timeslot 1. The characters of thetwo signals USF_TN0 and USF_TN1 must differ and must be distinguishableby the mobile station.

[0040] It is not necessary to add extra information elements to indicatewhen the Shifted USF mechanism is to be used, as it may be made implicitin the timeslot allocations for the particular multislot class of themobile station. Therefore no increase in signalling overhead would berequired.

[0041] With reference to FIG. 5, another example of an allocationenabled by implementation of a shifted USF is illustrated in FIG. 5. Theapplication is a class 7 MS with three uplink slots allocated. The USFon downlink slot 1 allocating the 3 uplink slots indicates that thefirst uplink slot available is uplink slot 0 rather than the usual slot1. This provides for the Ttb and Tra periods (as required by table 1)and as indicated in FIG. 5 at D and E respectively. The allocation wouldnot previously have been available for want of a sufficient period forTra.

[0042] The 2 slot allocation illustrated in FIG. 6 reverts to normaloperation i.e. the USF is not shifted. There are no physical constraintsin normal allocations for this 2 slot arrangement of FIG. 6 and thestandard USF in time slot 1 allocates uplink slots beginning with uplinkslot number 1.

[0043] Alternatively it may be convenient to apply positive signallingof the shift in position of the uplink allocation and an implementationof a shifted USF in a mobile station operating extended dynamicallocation is illustrated in FIG. 7. It should be noted that theindication (2) in FIG. 7 may be explicit (i.e. extra signalling) orimplicit (automatic for particular multislot class configuration). Withreference to FIG. 7, the mobile station receives at 1 an assignment ofuplink resources and USF's from the network. If at 2, an indication touse a shifted USF is detected then, for the first USF, the seconddownlink slot is monitored (3) otherwise the first downlink slot ismonitored (4). In either case, when a valid USF has been received at 5then uplink transmissions are initiated in the first uplink slot fromthe mobile station (6). When no valid USF has been received at 5 thenthe second downlink slot is monitored for a second USF at 7 and if valid(8) then uplink transmissions are initiated in the second uplink slot(9).

[0044] In the examples illustrated in FIGS. 2 to 6 the allocations aresteady state such that the allocations shown are maintained from frameto frame. The invention is not restricted to steady state allocationsand may be applied also to control of uplink resources that change fromone frame to another.

[0045] Examples of transitions are illustrated in FIGS. 8 and 9. Thesefigures each represent four consecutive frames but have been split forpresentation.

[0046]FIG. 8 illustrates the transition from one uplink slot allocationto five uplink slots allocation, for a Class 34 mobile. The first (top)two frames show steady state operation with one slot and the next(bottom) two frames show the transitional frames. For this transitionthe slot location of the USF is changed.

[0047]FIG. 9 illustrates the transition from four uplink slots to fiveuplink slots, for a Class 34 mobile. The first two frames show steadystate operation with four slots and the next two frames show thetransitional frames. For this transition the USF slot location isconstant but the value of the USF is changed.

[0048] In order to implement the invention in GPRS for example a table(Table 2) may be constructed for a Type 1 MS to allow extended dynamicallocation using the principles below:

[0049] In the case of extended dynamic allocation it is desirable forthe MS tobe able to “transmit up to its physical slot limit”;specifically, the MS should be able to transmit the maximum number ofslots possible according to the limitation of its multislot class, whilecontinuing to receive and decode the USF value on exactly one slot andperforming measurements. If it is not possible to define a multislotconfiguration which permits the MS to “transmit up to its physical slotlimit” using T_(ra), but it would be possible by using T_(ta), thenT_(ta) shall be used.

[0050] If it is not possible to define a multislot configuration forextended dynamic allocation which permits the MS to “transmit up to itsphysical slot limit” but it would be possible by using the shifted USFmechanism, then shifted USF shall be used. In this case T_(ra) will beused as first preference, but if this is not possible T_(ta) will beused as second preference. TABLE 2 T_(ra) T_(ta) Applicable Medium shallshall Multislot access mode No of Slots apply apply classes Note Uplink,1-3 Yes — 1-12, 19-45 Ext. Dynamic 4 No Yes 33-34, 2 38-39, 43-45 5 Yes— 34, 39 5 5 No Yes 44-45 2, 4 6 No Yes 45 5 Down + up, d + u = 2 − 4Yes — 1-12, 19-45 Ext. Dynamic d + u = 5, d > 1 Yes — 8-12, 19-45 d = 1,u = 4 No Yes 30-45 2 d + u = 6, d > 1 Yes 30-45 2, 3 d = 1, u = 5 Yes34,39 5 d + u = 7, d > 1 No Yes 40-45 2, 4 d = 1, u = 6 No Yes 45 5

1-22. (Canceled).
 23. A multiple access communication method for amobile station, comprising the steps of: receiving an uplink status flag(USF) on a downlink slot; monitoring the downlink slot to detect theUSF; and performing transmission on an uplink slot assigned by the USF,wherein the transmission is performed on a first uplink slot not only ifa USF for assigning the first uplink slot is detected on a firstdownlink slot but also if the USF for assigning the first uplink slot isdetected on a second downlink slot.
 24. The method according to claim23, wherein the transmission is performed on the first uplink slot andall consecutive uplink slots allocated for uplink transmission if theUSF for assigning the first uplink slot is detected.
 25. The methodaccording to claim 23, wherein the transmission is performed on an nth(n being an integer) uplink slot if a USF for assigning the nth uplinkslot is detected on an nth downlink slot.
 26. The method according toclaim 25, wherein the transmission is performed on the nth uplink slotand all consecutive uplink slots allocated for uplink transmission ifthe USF for assigning the nth uplink slot is detected on the nthdownlink slot.
 27. The method according to claim 23, wherein eightconsecutive uplink slots form an uplink TDMA frame and eight consecutivedownlink slots form a downlink TDMA frame.
 28. The method according toclaim 27, wherein if a USF for assigning an nth (n being an integer)uplink slot is detected on an nth downlink slot of a present downlinkTDMA frame, the transmission is performed on the nth uplink slot of anext uplink TDMA frame or consecutive group of uplink TDMA frames. 29.The method according to claim 27, wherein an offset between the uplinkTDMA frame and the downlink TDMAS frame is three slots or approximatelythree slots.
 30. The method according to claim 23, further comprisingthe step of performing adjacent cell signal level measurement andpreparation for reception prior to re-configuration from transmission toreception.
 31. The method according to claim 30, wherein the time neededfor performing adjacent cell signal level measurement and preparationfor reception is three slots.
 32. The method according to claim 30,wherein the time needed for performing adjacent cell signal levelmeasurement and preparation for reception is one slot.
 33. The methodaccording to claim 30, wherein the time needed for performing adjacentcell signal level measurement and preparation for reception is one slotand thirty one symbol periods timing advance offset.
 34. The methodaccording to claim 23, further comprising the step of: performingadjacent cell signal level measurement and preparation for receptionprior to re-configuration from reception to transmission, wherein thetime needed for performing adjacent cell signal level measurement andpreparation for transmission is one slot.
 35. The method according toclaim 31, wherein three slots are allocated for the uplink transmissionin the uplink TDMA frame.
 36. The method according to claim 32, whereinfive slots are allocated for the uplink transmission in the uplink TDMAframe.
 37. The method according to claim 33, wherein five slots areallocated for the uplink transmission in the uplink TDMA frame.
 38. Themethod according to claim 34, wherein six slots are allocated for theuplink transmission in the uplink TDMA frame.
 39. The method accordingto claim 23, wherein the number of multi-slot class is any one ofmulti-slot classes 7, 34, 39 and
 45. 40. A mobile station apparatus formultiple access communication, comprising: a reception section thatreceives an uplink status flag (USF) on a downlink slot; a detectionsection that monitors the downlink slot to detect the USF; and atransmission section that performs transmission on an uplink slotassigned by the USF, wherein the transmission section performstransmission on a first uplink slot not only if a USF for assigning thefirst uplink slot is detected on a first downlink slot but also if theUSF for assigning the first uplink slot is detected on a second downlinkslot.
 41. The apparatus according to claim 40, wherein the transmissionsection performs the transmission on the first uplink slot and allconsecutive uplink slots allocated for uplink transmission if the USFfor assigning the first uplink slot is detected.
 42. The apparatusaccording to claim 40, wherein the transmission section performs thetransmission on an nth (n being an integer) uplink slot if a USF forassigning the nth uplink slot is detected on an nth downlink slot. 43.The apparatus according to claim 42, wherein the transmission sectionperforms the transmission on the nth uplink slot and all consecutiveuplink slots allocated for uplink transmission if the USF for assigningthe nth uplink slot is detected on the nth downlink slot.
 44. Theapparatus according to claim 40, wherein eight consecutive uplink slotsform an uplink TDMA frame and eight consecutive downlink slots form adownlink TDMA frame.
 45. The apparatus according to claim 44, wherein ifa USF for assigning an nth (n being an integer) uplink slot is detectedon an nth downlink slot of a present downlink TDMA frame, thetransmission is performed on the nth uplink slot of a next uplink TDMAframe or consecutive group of uplink TDMA frames.
 46. The apparatusaccording to claim 44, wherein an offset between the uplink TDMA frameand the downlink TDMA frame is three slots or approximately three slots.47. The apparatus according to claim 40, further comprising: apreparation section that prepares for reception prior tore-configuration from transmission to reception; and a measurementsection that performs adjacent cell signal level measurement prior tore-configuration from transmission to reception or prior tore-configuration from reception to transmission.
 48. The apparatusaccording to claim 47, wherein the measurement section performs adjacentcell signal level measurement prior to re-configuration fromtransmission to reception and the time needed for performing adjacentcell signal level measurement and preparation for reception is threeslots.
 49. The apparatus according to claim 47, wherein the measurementsection performs adjacent cell signal level measurement prior tore-configuration from transmission to reception and the time needed forperforming adjacent cell signal level measurement and preparation forreception is one slot.
 50. The apparatus according to claim 47, whereinthe measurement section performs adjacent cell signal level measurementprior to re-configuration from transmission to reception and the timeneeded for performing adjacent cell signal level measurement andpreparation for reception is one slot and thirty one symbol periodstiming advance offset.
 51. The apparatus according to claim 47, whereinthe measurement section performs adjacent cell signal level measurementprior to re-configuration from reception to transmission and the timeneeded for performing adjacent cell signal level measurement andpreparation for transmission is one slot.
 52. The apparatus according toclaim 48, wherein three slots are allocated for the uplink transmissionin the uplink TDMA frame.
 53. The apparatus according to claim 49,wherein five slots are allocated for the uplink transmission in theuplink TDMA frame.
 54. The apparatus according to claim 50, wherein fiveslots are allocated for the uplink transmission in the uplink TDMAframe.
 55. The apparatus according to claim 51, wherein six slots areallocated for the uplink transmission in the uplink TDMA frame.
 56. Theapparatus according to claim 51, wherein the number of multi-slot classis one of multi-slot classes 7, 34, 39 and 45.